This paper discusses the findings of an experimental study on the effect of various curing procedures on the compressive strength of concrete produced by partially substituting portland cement with Palm Kernel S...This paper discusses the findings of an experimental study on the effect of various curing procedures on the compressive strength of concrete produced by partially substituting portland cement with Palm Kernel Shell Ash(PKSA).Palm kernel shell ash was utilized in a 1:2:4 mix ratio as a partial substitute for ordinary Portland cement(OPC)at percentage levels of 0%,10%,and 15%.River sand with particles passing a 4.75 mm BS sieve was used,as well as crushed aggregate with a maximum size of 20 mm,and palm kernel shell ash with particles passing a 212μm sieve.The compressive strength of the test cubes(150 mm × 150 mm × 150 mm)was determined after 7,28,and 56 days of curing.The results demonstrated that test cubes containing Palm kernel shell ash developed strength over a longer curing period than ordinary Portland cement concrete samples and that the strength changes depending on the amount of PKSA in the cube samples.The findings showed that at 28 days,test cubes with 5%,10%,and 15%PKSA content in all curing procedures utilized obtained a greater compressive strength.Curing by immersion produced the highest compressive strength in all replacement level while the concrete cured by sprinkling and spraying gives a lower strength in all replacement level.展开更多
The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction...The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction method is using expansive shotcrete mixture consisting of calcium sulfoaluminate cement(CSA), ordinary Portland cement(OPC), and calcium sulfate(CS) to reduce shrinkage. Furthermore, fibers can be added to the mixture to restrain expansion and impede cracking. The objective of this paper is to study the effects of nylon fiber, glass fiber, and steel fiber on an expansive shotcrete mixture that can better resist cracking. In this study, parameters such as density, water absorption, volume of permeable voids, unconfined compressive strength(UCS), splitting tensile strength(STS), and volume change of fiber-added expansive mixtures were determined at different time periods(i.e. the strengths on the 28 th day, and the volume changes on the 1 st, 7 th, 14 th, 21 st, and 28 th days). The results show that addition of fibers can improve mixture durability, in the form of decreased water absorption and reduced permeable pore space content. Moreover, the expansion of the CSA-OPC-CS mixture was restrained up to50% by glass fiber, up to 43% by nylon fiber, and up to 28% by steel fiber. The results show that the STS was improved by 57% with glass fiber addition, 43% with steel fiber addition, and 38% with nylon fiber addition. The UCS was also increased by 31% after steel fiber addition, 26% after nylon fiber addition, and16% after glass fiber addition. These results suggest that fiber additions to the expansive shotcrete mixtures can improve durability and strengths while controlling expansion.展开更多
The poor quality of Kenyan in situ concrete has necessitated research to establish the properties of the ingredient materials and their influence on the troubling rate of failure of reinforced concrete structures in t...The poor quality of Kenyan in situ concrete has necessitated research to establish the properties of the ingredient materials and their influence on the troubling rate of failure of reinforced concrete structures in the country during construction and usage. The compressive strength of concrete relies on the properties of the constituent materials, proportions of the mixture, workmanship, compaction method and curing conditions. This paper outlines findings of an experimental investigation on the properties of Kenyan concrete ingredient materials and their influence on the compressive strength of concrete in Kenya. Three types of cements (42.5N, 32.5R, 32.5N) from six different cement manufacturers and fine aggregates from three different regions in the country were used during the study. Cements and aggregates chemical analysis was done using the Atomic Absorption Spectrometer machine while the physical and the mechanical properties were checked based on the British Standards. The British DOE concrete mix design method was used to generate the concrete mix proportion and concrete was tested for early and ultimate compressive strengths at 7, 14 and 28 days. It was observed that the different cement brands have varying properties with CEM A having the highest ultimate compressive and flexural strengths. It was further noted that aggregates from the coastal region produced concrete of higher compressive strengths. When the commonly used mix design method was adopted, blended Portland cements produced concrete with ultimate compressive strengths lower than the designed target strengths. The study therefore recommends the development of a concrete mix design procedure for blended cement concrete production in Kenya.展开更多
This work examined the structural properties of concrete obtained by partially replacing cement with sawdust ash.The sawdust ash which is a pozzolan was obtained by burning sawdust which is a waste product from proces...This work examined the structural properties of concrete obtained by partially replacing cement with sawdust ash.The sawdust ash which is a pozzolan was obtained by burning sawdust which is a waste product from processing of timber in an open air.The burnt ash was passed through a 150μm metric sieve to obtain the ash used.Physical and chemical analysis were performed on the ash to verify its suitability as a partial substitute for cement in concrete.Chemical analysis was also carried out on the Ordinary Portland Cement(OPC)sample.Concrete mixes were produced by replacing OPC with 0%,5%,10%,20%and 30%of Sawdust Ash(SDA).Both fresh and hardened properties of the concrete produced were investigated.The chemical investigation on the ash showed that it contained most of the basic compounds found in OPC making it suitable to serve as a partial substitute for OPC in concrete.Investigation on the concrete showed that both the workability and density of the concrete reduce as the SDA content increases.Analysis on the hardened concrete revealed that the compressive strength of the concrete decreases as the ash content increases for the early ages of curing.However,from 21 days curing age upwards,the compressive strength decreases as SDA increases up to 10%of SDA at which the compressive strength rose to a maximum value,and then starts reducing again as the percentage SDA increases.Thus,the SDA concrete gained rapid strength at later ages indicating its pozzolanic activity.展开更多
A vast amount of construction and demolition(C&D)wastes are generated in Western Australia(WA)of which a major portion goes to landfills.The diversion of C&D waste from landfills would be the single most signi...A vast amount of construction and demolition(C&D)wastes are generated in Western Australia(WA)of which a major portion goes to landfills.The diversion of C&D waste from landfills would be the single most significant opportunity for WA to improve its recovery performance.C&D waste materials have already been investigated for their appropriateness and use in pavement and concrete.This work is the continuation of the authors’previous work involving further experimental tests to prove the structural suitability of a building’s structural member(i.e.,beam)made of recycled aggregates and industrial by-products.The concrete mixes considered in this study are 100NA+100 OPC(Control),100RA+100OPC,50RA+50NA+90OPC+10SF and 50RA+50NA+60OPC+30FA+10SF.The Reinforced Concrete(RC)beam made of 50RA+50NA+60OPC+30FA+10SF concrete mix was found to be the only eco-efficient option.This option has reduced the level of environmental impacts in a cost-competitive manner.The use of this eco-efficient option could also provide new employment opportunities and significant improvements in terms of land and energy resources conservation and bio-diversity enhancement.展开更多
Since last two decades,the Portland Pozzolane Cement(PPC)is extensively used in structural concrete.But,till to date,a few literature is available on bond strength of concrete using PPC mixes.There are many literature...Since last two decades,the Portland Pozzolane Cement(PPC)is extensively used in structural concrete.But,till to date,a few literature is available on bond strength of concrete using PPC mixes.There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement(OPC).Hence,a comparative study was conducted on bond strength between OPC and PPC mixes.In the present investigation,total 24 samples consisting of M20,M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days.The pullout bond test was conducted on each specimen as per IS:2770-1967/1997[1]and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress.It was observed that the critical bond strength of PPC mixes is 10%higher than OPC mixes.Whereas,marginal improvement was noticed in maximum bond strength of PPC mixes.Hence,based on these findings,it could be concluded that development length for PPC mixes could be reduced by 10%as compared with same grade of OPC mixes.展开更多
为了研究玄武岩纤维对不同胶凝材料混凝土的强韧化效应,制备了玄武岩纤维增强普通硅酸盐水泥混凝土BFROPCC与玄武岩纤维增强地质聚合物混凝土BFRGC。采用Φ100 mm SHPB试验装置,分别研究了BFROPCC与BFRGC的冲击力学性能,并分析了玄武岩...为了研究玄武岩纤维对不同胶凝材料混凝土的强韧化效应,制备了玄武岩纤维增强普通硅酸盐水泥混凝土BFROPCC与玄武岩纤维增强地质聚合物混凝土BFRGC。采用Φ100 mm SHPB试验装置,分别研究了BFROPCC与BFRGC的冲击力学性能,并分析了玄武岩纤维对普通硅酸盐水泥混凝土OPCC与地质聚合物混凝土GC的强韧化效应。结果表明:BFROPCC与BFRGC的强度和韧性随应变率的增加而提高,其应变率敏感值分别为29.5、40.9 s-1;玄武岩纤维对于OPCC的增强效果优于GC,当纤维掺量为0.1%时,纤维对于OPCC的增强和增韧效果相对较好;玄武岩纤维不适于用来增强GC,当纤维掺量为0.3%时,纤维对于GC的增韧效果相对较好。展开更多
文摘This paper discusses the findings of an experimental study on the effect of various curing procedures on the compressive strength of concrete produced by partially substituting portland cement with Palm Kernel Shell Ash(PKSA).Palm kernel shell ash was utilized in a 1:2:4 mix ratio as a partial substitute for ordinary Portland cement(OPC)at percentage levels of 0%,10%,and 15%.River sand with particles passing a 4.75 mm BS sieve was used,as well as crushed aggregate with a maximum size of 20 mm,and palm kernel shell ash with particles passing a 212μm sieve.The compressive strength of the test cubes(150 mm × 150 mm × 150 mm)was determined after 7,28,and 56 days of curing.The results demonstrated that test cubes containing Palm kernel shell ash developed strength over a longer curing period than ordinary Portland cement concrete samples and that the strength changes depending on the amount of PKSA in the cube samples.The findings showed that at 28 days,test cubes with 5%,10%,and 15%PKSA content in all curing procedures utilized obtained a greater compressive strength.Curing by immersion produced the highest compressive strength in all replacement level while the concrete cured by sprinkling and spraying gives a lower strength in all replacement level.
基金financial support from Natural Sciences and Engineering ResearchCouncil(NSERC)(NSERC EGP 501335-16) along with the donated CSA cement
文摘The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction method is using expansive shotcrete mixture consisting of calcium sulfoaluminate cement(CSA), ordinary Portland cement(OPC), and calcium sulfate(CS) to reduce shrinkage. Furthermore, fibers can be added to the mixture to restrain expansion and impede cracking. The objective of this paper is to study the effects of nylon fiber, glass fiber, and steel fiber on an expansive shotcrete mixture that can better resist cracking. In this study, parameters such as density, water absorption, volume of permeable voids, unconfined compressive strength(UCS), splitting tensile strength(STS), and volume change of fiber-added expansive mixtures were determined at different time periods(i.e. the strengths on the 28 th day, and the volume changes on the 1 st, 7 th, 14 th, 21 st, and 28 th days). The results show that addition of fibers can improve mixture durability, in the form of decreased water absorption and reduced permeable pore space content. Moreover, the expansion of the CSA-OPC-CS mixture was restrained up to50% by glass fiber, up to 43% by nylon fiber, and up to 28% by steel fiber. The results show that the STS was improved by 57% with glass fiber addition, 43% with steel fiber addition, and 38% with nylon fiber addition. The UCS was also increased by 31% after steel fiber addition, 26% after nylon fiber addition, and16% after glass fiber addition. These results suggest that fiber additions to the expansive shotcrete mixtures can improve durability and strengths while controlling expansion.
文摘The poor quality of Kenyan in situ concrete has necessitated research to establish the properties of the ingredient materials and their influence on the troubling rate of failure of reinforced concrete structures in the country during construction and usage. The compressive strength of concrete relies on the properties of the constituent materials, proportions of the mixture, workmanship, compaction method and curing conditions. This paper outlines findings of an experimental investigation on the properties of Kenyan concrete ingredient materials and their influence on the compressive strength of concrete in Kenya. Three types of cements (42.5N, 32.5R, 32.5N) from six different cement manufacturers and fine aggregates from three different regions in the country were used during the study. Cements and aggregates chemical analysis was done using the Atomic Absorption Spectrometer machine while the physical and the mechanical properties were checked based on the British Standards. The British DOE concrete mix design method was used to generate the concrete mix proportion and concrete was tested for early and ultimate compressive strengths at 7, 14 and 28 days. It was observed that the different cement brands have varying properties with CEM A having the highest ultimate compressive and flexural strengths. It was further noted that aggregates from the coastal region produced concrete of higher compressive strengths. When the commonly used mix design method was adopted, blended Portland cements produced concrete with ultimate compressive strengths lower than the designed target strengths. The study therefore recommends the development of a concrete mix design procedure for blended cement concrete production in Kenya.
文摘This work examined the structural properties of concrete obtained by partially replacing cement with sawdust ash.The sawdust ash which is a pozzolan was obtained by burning sawdust which is a waste product from processing of timber in an open air.The burnt ash was passed through a 150μm metric sieve to obtain the ash used.Physical and chemical analysis were performed on the ash to verify its suitability as a partial substitute for cement in concrete.Chemical analysis was also carried out on the Ordinary Portland Cement(OPC)sample.Concrete mixes were produced by replacing OPC with 0%,5%,10%,20%and 30%of Sawdust Ash(SDA).Both fresh and hardened properties of the concrete produced were investigated.The chemical investigation on the ash showed that it contained most of the basic compounds found in OPC making it suitable to serve as a partial substitute for OPC in concrete.Investigation on the concrete showed that both the workability and density of the concrete reduce as the SDA content increases.Analysis on the hardened concrete revealed that the compressive strength of the concrete decreases as the ash content increases for the early ages of curing.However,from 21 days curing age upwards,the compressive strength decreases as SDA increases up to 10%of SDA at which the compressive strength rose to a maximum value,and then starts reducing again as the percentage SDA increases.Thus,the SDA concrete gained rapid strength at later ages indicating its pozzolanic activity.
文摘A vast amount of construction and demolition(C&D)wastes are generated in Western Australia(WA)of which a major portion goes to landfills.The diversion of C&D waste from landfills would be the single most significant opportunity for WA to improve its recovery performance.C&D waste materials have already been investigated for their appropriateness and use in pavement and concrete.This work is the continuation of the authors’previous work involving further experimental tests to prove the structural suitability of a building’s structural member(i.e.,beam)made of recycled aggregates and industrial by-products.The concrete mixes considered in this study are 100NA+100 OPC(Control),100RA+100OPC,50RA+50NA+90OPC+10SF and 50RA+50NA+60OPC+30FA+10SF.The Reinforced Concrete(RC)beam made of 50RA+50NA+60OPC+30FA+10SF concrete mix was found to be the only eco-efficient option.This option has reduced the level of environmental impacts in a cost-competitive manner.The use of this eco-efficient option could also provide new employment opportunities and significant improvements in terms of land and energy resources conservation and bio-diversity enhancement.
文摘Since last two decades,the Portland Pozzolane Cement(PPC)is extensively used in structural concrete.But,till to date,a few literature is available on bond strength of concrete using PPC mixes.There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement(OPC).Hence,a comparative study was conducted on bond strength between OPC and PPC mixes.In the present investigation,total 24 samples consisting of M20,M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days.The pullout bond test was conducted on each specimen as per IS:2770-1967/1997[1]and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress.It was observed that the critical bond strength of PPC mixes is 10%higher than OPC mixes.Whereas,marginal improvement was noticed in maximum bond strength of PPC mixes.Hence,based on these findings,it could be concluded that development length for PPC mixes could be reduced by 10%as compared with same grade of OPC mixes.
文摘为了研究玄武岩纤维对不同胶凝材料混凝土的强韧化效应,制备了玄武岩纤维增强普通硅酸盐水泥混凝土BFROPCC与玄武岩纤维增强地质聚合物混凝土BFRGC。采用Φ100 mm SHPB试验装置,分别研究了BFROPCC与BFRGC的冲击力学性能,并分析了玄武岩纤维对普通硅酸盐水泥混凝土OPCC与地质聚合物混凝土GC的强韧化效应。结果表明:BFROPCC与BFRGC的强度和韧性随应变率的增加而提高,其应变率敏感值分别为29.5、40.9 s-1;玄武岩纤维对于OPCC的增强效果优于GC,当纤维掺量为0.1%时,纤维对于OPCC的增强和增韧效果相对较好;玄武岩纤维不适于用来增强GC,当纤维掺量为0.3%时,纤维对于GC的增韧效果相对较好。
